Monolithic multicolor light-emitting diodes and LED backlights

Abstract

This invention provides monolithic multicolor light-emitting diodes and LED backlights that can reduce the cost of RGB-LED backlights. [Solution] The monolithic multicolor light-emitting diode includes a multicolor light-emitting layer provided between an N-type layer and a P-type layer. The multicolor light-emitting layer includes a first light-emitting layer that emits light of a first color and a second light-emitting layer that emits light of a second color. Here, the peak wavelength λ of the light of the second color p2 The peak wavelength λ of the first color of light p1 Larger than and λ p2 -λ p1 The wavelength is ≥50nm. The thickness of the second well layer in the second light-emitting layer is less than the thickness of the first well layer in the first light-emitting layer. The monolithic multicolor light-emitting diode can emit at least two colors of light, eliminating the use of fluorescent powder or reducing its usage, thereby lowering the cost of RGB-LED backlights.

Description

[Technical Field]

[0001] The present invention relates to the field of light-emitting diodes, and more specifically to monolithic multicolor light-emitting diodes and LED backlights. [Background technology]

[0002] Light-emitting diodes (LEDs) based on gallium nitride (GaN) III-V compound semiconductors typically exhibit extremely excellent luminescence characteristics. Theoretically, LED light emission composed of GaN-based III-V compound semiconductors such as InGaN, AlGaN, AlInGaN, and GaN can cover the entire visible spectrum from short wavelengths (i.e., UV) to long wavelengths (i.e., red light), and is therefore widely used in fields such as traffic lights, vehicle lights, landscape and interior lighting sources, and displays. Currently, LED backlights used in displays are classified into RGB-LEDs and white LEDs. Here, RGB-LEDs are packages of three types of monochromatic LED chips: blue, green, and red. For example, the blue and green LED chips are III nitride compound semiconductor elements, and the red light-emitting element is a GaAs-based or GaN-based light-emitting element. On the other hand, white LEDs are formed by combining monochromatic LED chips with fluorescent powders; for example, a monochromatic blue chip can be combined with green and red fluorescent powders, or a monochromatic blue LED chip can be combined with yellow fluorescent powders. Among these, RGB three-primary-color LED backlights offer the best display effect, but are expensive. White LEDs require the use of fluorescent powders, and as shown in Figure 1, the NTSC (National Television Standards Committee) color gamut produced by different fluorescent powder formulations not only exhibits clear differences in itself, but also makes it relatively difficult to control the uniformity after mixing the fluorescent powder with the resin. This leads to problems such as poor light emission uniformity, poor color tone consistency, tendency for color temperature to shift, and color rendering that is not sufficiently ideal.

[0003] The NTSC color gamut is known to be the ratio of a certain triangular region under the NTSC standard to the standard triangular region. A higher ratio indicates better color reproduction, and in the industry, high color gamut coverage refers to an NTSC color gamut ratio of ≥ 85%. Generally, high color gamut coverage white light is achieved by a blue light chip + green fluorescent powder + red fluorescent powder. Currently, the green fluorescent powder in the best formulation for achieving high color gamut coverage is β-SiAlON, but its full width at half maximum is still 48nm to 55nm (see Figure 2).

[0004] Therefore, how to reduce the cost of RGB-LED backlights and / or reduce the use of fluorescent powders in white LED backlights while maintaining high NTSC standards are currently technical challenges that need to be addressed.

[0005] In light of this, we have proposed the present invention. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The first object of the present invention is to provide a monolithic multicolor light-emitting diode that can emit at least two colors of light on a single LED chip and can reduce the cost of RGB-LED backlights by eliminating or reducing the use of fluorescent powder.

[0007] A second object of the present invention is to provide an LED backlight. [Means for solving the problem]

[0008] To achieve the above objectives of the present invention, the following technical means are employed.

[0009] The present invention first provides a monolithic multicolor light-emitting diode comprising a multicolor light-emitting layer provided between an N-type layer and a P-type layer. The multicolor light-emitting layer includes a first light-emitting layer that emits light of a first color and a second light-emitting layer that emits light of a second color, wherein the peak wavelength of the light of the second color is λp2 is greater than the peak wavelength λ of the light of the first color p1 and λ p2 −λ p1 ≧50 nm, and the thickness of the second well layer in the second light-emitting layer is less than the thickness of the first well layer in the first light-emitting layer. Preferably, the ratio of the thickness of the second well layer to the thickness of the first well layer is 0.5 to 0.95. Preferably, the thickness of the second well layer is 27 to 32 Å. Preferably, the thickness of the first well layer is 33 to 38 Å. Preferably, the first well layer contains In x1 Ga (1-x1) N, and the second well layer contains In x2 Ga (1-x2) N, where 1 > X2 > X1 > 0.1. Preferably, X2 = 0.22 to 0.28. Preferably, X1 = 0.13 to 0.19. Preferably, the light of the first color contains blue light, and the light of the second color contains green light. Preferably, the peak wavelength λ of the light of the first color p1 = 440 to 470 nm. Preferably, the peak wavelength λ of the light of the second color p2 = 520 to 550 nm. Preferably, when the input current is 10 mA or more, the ratio of the peak wavelength intensity of the light of the first color to the peak wavelength intensity of the light of the second color is 5 or more. Preferably, the second light-emitting layer includes a second barrier layer, and the first light-emitting layer includes a first barrier layer. Preferably, the thickness of the second barrier layer is greater than the thickness of the first barrier layer. Preferably, the thickness of the second barrier layer is 100 to 200 Å. Preferably, the thickness of the first barrier layer is 90 to 100 Å. Preferably, the ratio H2 / H1 = 0.9 to 1.1 is the ratio of the sum of the thicknesses H$ of the second well layer and the second barrier layer to the sum of the thicknesses H1 of the first well layer and the first barrier layer. Preferably, the ratio H3 of the thicknesses of the second barrier layer and the second well layer is equal to or greater than the ratio H4 of the thicknesses of the first barrier layer and the first well layer, and H3 / H4 = 1 to 2. Preferably, the first barrier layer in the first light-emitting layer includes at least one of GaN, AlGaN, or InAlGaN. Preferably, the second barrier layer in the second light-emitting layer comprises at least one of GaN, AlGaN, or InAlGaN. Preferably, the number of the first well layers is 10 to 20, and a first barrier layer is provided between two adjacent first well layers. Preferably, the number of the second well layers is 1 to 5, and a second barrier layer is provided on both sides of each of the second well layers. Preferably, the first light-emitting layer includes a first periodic structure in which a first well layer and a first barrier layer are alternately stacked, and the number of periods of the first periodic structure is 10 to 20. Preferably, the second light-emitting layer includes a second periodic structure in which a second well layer and a second barrier layer are alternately stacked, and the number of periods of the second periodic structure is 1 to 5. Preferably, the number of the first well layers is 4 to 20 times the number of the second well layers. Preferably, the energy band of the second well layer in the second light-emitting layer is lower than the energy band of the first well layer in the first light-emitting layer. Preferably, the energy band of the second barrier layer in the second light-emitting layer is lower than the energy band of the first barrier layer in the first light-emitting layer. Preferably, when the direction from the N-type layer to the P-type layer is defined as the first direction, the energy band of the second barrier layer in the second light-emitting layer changes from low to high in the first direction, and the energy band of the first barrier layer in the first light-emitting layer changes from high to low in the first direction. Preferably, Al is doped between the second well layer and the second barrier layer in the second light-emitting layer. Preferably, the thickness of the region doped with Al is less than 1 / 3 of the thickness of the second well layer. Preferably, when the injection current is 350 mA, the luminance of the monolithic multicolor light-emitting diode is 770 mW or more. The present invention further provides an LED backlight. The LED backlight includes an RGB-LED and a white LED, and the RGB-LED or the white LED includes the monolithic multicolor light-emitting diode. Preferably, the RGB-LED includes the monolithic multicolor light-emitting diode and a monochromatic red light-emitting diode. Preferably, the white LED includes the monolithic multicolor light-emitting diode, a fluorescent film layer, and a reflective sealing layer provided around the monolithic multicolor light-emitting diode and the fluorescent film layer. Here, the fluorescent film layer includes a silicone layer and a red fluorescent layer, and the red fluorescent powder in the red fluorescent layer includes a nitride fluorescent powder and / or a fluoride fluorescent powder. When the red fluorescent powder is a fluoride fluorescent powder, a silicone protective layer is further provided on the side of the red fluorescent layer far from the monolithic multicolor light-emitting diode.

Advantages of the Invention

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows.

[0011] (1) The monolithic multicolor light-emitting diode provided by the present invention can emit at least two colors of light, does not use a fluorescent powder or reduces the usage amount thereof, and reduces the cost of the RGB-LED backlight.

[0012] (2) The monolithic multicolor light-emitting diode provided by the present invention solves the problem that the crystal quality of the buffer layer and the light-emitting layer of the epitaxial growth is poor, which causes an increase in non-radiative recombination and thereby reduces the internal quantum efficiency of the light-emitting element.

[0013] (3) When the monolithic multicolor light-emitting diode provided by the present invention is applied to an LED backlight, the monolithic multicolor light-emitting diode and a monocolor red light-emitting diode are packaged together to form an LED backlight, or the monolithic multicolor light-emitting diode and red fluorescent powder are packaged together to obtain a white LED backlight, or the monolithic multicolor light-emitting diode forms a light-emitting diode that simultaneously emits red, green, and blue on a single chip, thereby obtaining an LED backlight with a wide color gamut and high brightness.

[0014] (4) The monolithic multicolor light-emitting diode provided by the present invention can improve crystal quality by reducing the thickness of the blue light quantum barrier layer (thickness of the first barrier layer).

[0015] (5) The monolithic multicolor light-emitting diode provided by the present invention can reduce energy band distortion and improve the average energy band by employing a thick barrier + thin well structure in the second light-emitting layer.

[0016] (6) The monolithic multicolor light-emitting diode provided by the present invention can improve luminous efficiency by bringing the average energy bands of the first light-emitting layer and the second light-emitting layer closer together by setting H3 / H4 = 1 to 2.

[0017] (7) The monolithic multicolor light-emitting diode provided by the present invention has a chip brightness that is superior to that of an LED chip in which the thickness of the blue light well and the green light well are the same, by setting the thickness of the second well layer to the thickness of the first well layer, and the brightness is improved by at least 10%. [Brief explanation of the drawing]

[0018] To more clearly describe specific embodiments of the present invention or technical means in the prior art, the drawings used in the description of specific embodiments or the prior art will be briefly described below. Note that the drawings in the following description represent only some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these without requiring any creative effort. [Figure 1] This figure shows proposed realization methods for white light with different NTSC values ​​provided by the present invention. [Figure 2] This figure shows the peak wavelength and full width at half maximum parameters of different LED fluorescent powder systems provided by the present invention. [Figure 3] This is a schematic diagram of the first structure of a multicolor light-emitting layer provided by the present invention. [Figure 4] This is a schematic diagram of the second structure of the multicolor light-emitting layer provided by the present invention. [Figure 5] This is a schematic diagram of the third structure of the multicolor light-emitting layer provided by the present invention. [Figure 6] This is a schematic diagram of the fourth structure of the multicolor light-emitting layer provided by the present invention. [Figure 7] This is a schematic diagram of the fifth structure of the multicolor light-emitting layer provided by the present invention. [Figure 8] This is a schematic diagram of the sixth structure of the multicolor light-emitting layer provided by the present invention. [Figure 9] This is a schematic diagram of the structure of a monolithic multicolor light-emitting diode provided by the present invention. [Figure 10] This is a schematic cross-sectional diagram of the structure of a face-up type LED chip provided by the present invention. [Figure 11] This is a schematic cross-sectional diagram of the structure of a flip-chip type LED chip provided by the present invention. [Figure 12] This is a schematic diagram of the structure of a white LED provided by the present invention. [Figure 13] This is another schematic diagram of the structure of the white LED provided by the present invention. [Figure 14] This figure shows the optical power spectral distribution under different currents provided by the present invention. [Figure 15] This figure shows the normalized relative intensity spectrum of green light provided by the present invention. [Modes for carrying out the invention]

[0019] The technical means of the present invention will be clearly and completely described below with reference to the drawings and specific embodiments. However, it will be understood by those skilled in the art that the embodiments described below are only some, and not all, embodiments of the present invention. These are merely illustrative of the present invention and should not be considered to limit the scope of the invention. All other embodiments that can be obtained by those skilled in the art without creative work based on the embodiments of the present invention are all within the scope of the present invention. Unless specific conditions are specified in the embodiments, they should be carried out under normal conditions or conditions recommended by the manufacturer. Unless the manufacturer of the reagents or equipment used is specified, they should all be common products available on the market.

[0020] Unless otherwise specified, in this invention, "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used solely for explanatory purposes and should not be understood as indicating or implying relative importance or quantity, nor as implicitly indicating the importance or quantity of the indicated technical features. Furthermore, it should be understood that "first," "second," "third," "fourth," etc., serve only the purpose of a non-exclusive enumeration and do not constitute a closed limitation on quantity.

[0021] Unless otherwise specified, the terms "contains" and "equipped with" in this invention refer to open formulas, but may also refer to closed formulas. For example, the terms "contains" and "equipped with" may indicate that other components not listed may be included, or they may indicate that only the listed components are included.

[0022] Unless otherwise specified, in this invention, "one or more types" or "at least one type" refers to any one, any two, or any two or more of the listed items. Here, "multiple types" refers to any two or any two or more of the listed items.

[0023] In a first embodiment, the present invention provides a monolithic multicolor light-emitting diode. The monolithic multicolor light-emitting diode includes an N-type layer 110, a P-type layer 130, and a multicolor light-emitting layer 120 provided between the N-type layer 110 and the P-type layer 130. Here, the multi-color light-emitting layer 120 includes a first light-emitting layer 121 that emits light of a first color, and a second light-emitting layer 122 that emits light of a second color. Here, the peak wavelength λ of the second color of light p2 The peak wavelength λ of the first color of light is p1 Larger than and λ p2 -λ p1 It is ≥50nm. Here, .'' p2 -λ p1 The value includes, but is not limited to, one point or any two numbers within the range of 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 110nm, 120nm, 130nm, 140nm, and 150nm.

[0024] Furthermore, the thickness of the second well layer (referring to the thickness of a single layer) in the second light-emitting layer 122 is less than the thickness of the first well layer (referring to the thickness of a single layer) in the first light-emitting layer 121.

[0025] The single chip provided by the present invention can emit light-emitting diodes of various different colors, can emit at least two colors of light, eliminates or reduces the use of fluorescent powder, and reduces the cost of RGB-LED backlights.

[0026] LED emission based on GaN-based III-V compound semiconductors such as InGaN, AlGaN, AlInGaN, and GaN can cover the entire visible spectrum from short wavelengths (i.e., UV) to long wavelengths (i.e., red light). By adjusting the In concentration in the luminescence well layer, different colors / wavelengths of light are emitted, and theoretically, higher In concentrations result in longer wavelengths.

[0027] For example, in the case of a blue and green two-color LED chip, its core structure is formed by stacking and growing a green light MQW (quantum well) structure and a blue light MQW structure. Since the In concentration in the green light MQW is much higher than that in the blue light MQW, strong stress is generated internally when stacking and growing the two types of MQW structures, which degrades the growth quality and affects product performance. This invention solves the problem of poor crystal quality in the epitaxial growth buffer layer and light-emitting layer, leading to an increase in non-radiative recombination and consequently lowering the internal quantum efficiency of the light-emitting element, by controlling the thickness of the second well layer to be smaller than the thickness of the first well layer.

[0028] In some specific embodiments, the monolithic multicolor light-emitting diode provided by the present invention includes at least a green light-emitting layer and a blue light-emitting layer, and the light-emitting diode has a green light emission peak and a blue light emission peak after energization. That is, the first color of light described above includes blue light, and the second color of light described above includes green light.

[0029] When applied to LED backlights, the blue-green light-emitting diode and the monochromatic red light-emitting diode of the present invention are packaged together to form an LED backlight. Alternatively, the blue-green light-emitting diode and the red fluorescent powder of the present invention are packaged together to obtain a white LED backlight. Alternatively, the present invention can form a light-emitting diode capable of simultaneously emitting red, green, and blue light on a single chip. This results in an LED backlight with a wide color gamut and high brightness.

[0030] In some specific embodiments, the thickness ratio of the second well layer to the first well layer is 0.5 to 0.95, and includes, but is not limited to, any one point or range between any two of 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, and 0.95. Preferably, it is 0.8 to 0.9. Here, by adjusting the thickness ratio of the second well layer to the first well layer, the stress and crystal quality experienced in the MQW can be controlled, and consequently, the brightness can be adjusted.

[0031] In some specific embodiments, the thickness of the second well layer is 27–32 Å, including, but not limited to, one point or any two of 27 Å, 28 Å, 29 Å, 30 Å, 31 Å, and 32 Å.

[0032] In some specific embodiments, the thickness of the first well layer is 33–38 Å, and includes, but is not limited to, one point or any two of 33 Å, 34 Å, 35 Å, 36 Å, 37 Å, and 38 Å.

[0033] In some specific embodiments, the first well In x1 Ga (1-x1) The second well layer contains N, and the aforementioned second well layer is In x2 Ga (1-x2) N is included, where 1 > X2 > X1 > 0.1, i.e., the In concentration in the second well layer is greater than the In concentration in the first well layer. Here, the value of X2 or X1 includes, but is not limited to, one point or range between any two of 0.11, 0.13, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.6, 0.7, 0.8, 0.9.

[0034] By adjusting the In concentration in the luminescent well layer, light of different colors / wavelengths can be emitted. Theoretically, the higher the In concentration, the longer the wavelength.

[0035] In some specific embodiments, X2 = 0.22 to 0.28, and includes, but is not limited to, one point or any two points between 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, and 0.28.

[0036] In some specific embodiments, X1 = 0.13 to 0.19, and includes, but is not limited to, one point or a range value between any two of the following: 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, and 0.19.

[0037] In some specific embodiments, the first color of light includes blue light, and the second color of light includes green light.

[0038] In some specific embodiments, the peak wavelength λ of the first color light p1 =440=470nm, and includes, but is not limited to, any one point or range between any two of the following: 440nm, 450nm, 460nm, and 470nm.

[0039] In some specific embodiments, the peak wavelength λ of the second color light p2 = 520~550nm, which includes, but is not limited to, one point among 520nm, 530nm, 540nm, and 550nm, or a range value between any two of them.

[0040] In some specific embodiments, to satisfy the wide color gamut of the white LED, when the input current is 10 mA or more, the ratio of the peak wavelength intensity of the light of the first color to the peak wavelength intensity of the light of the second color is 5 or more, and includes, but is not limited to, any one point or any two of 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15. Preferably, it is 5 to 10.

[0041] In some specific embodiments, the thickness of the second barrier layer in the second light-emitting layer 122 (referring to the thickness of a single layer) is greater than the thickness of the first barrier layer in the first light-emitting layer 121 (referring to the thickness of a single layer). The present invention can improve crystal quality and increase brightness by reducing the thickness of the blue light quantum barrier layer (thickness of the first barrier layer).

[0042] In some specific embodiments, the thickness of the second barrier layer is 100 to 200 Å, and includes, but is not limited to, any one point or range between any two of the following values: 100 Å, 110 Å, 120 Å, 130 Å, 140 Å, 150 Å, 160 Å, 170 Å, 180 Å, 190 Å, and 200 Å.

[0043] In some specific embodiments, the thickness of the first barrier layer is 90 to 100 Å, and includes, but is not limited to, one point or any two of the following values: 90 Å, 91 Å, 92 Å, 93 Å, 94 Å, 95 Å, 96 Å, 97 Å, 98 Å, 99 Å, and 100 Å.

[0044] In some specific embodiments, the ratio H2 / H1 = 0.9 to 1.1 of the sum of the thicknesses H2 of the second well layer and the second barrier layer to the sum of the thicknesses H1 of the first well layer and the first barrier layer is 0.9 to 1.1, and includes, but is not limited to, any one point or range between any two of 0.9, 0.95, 1, 1.01, 1.03, 1.05, 1.06, 1.08, and 1.1. Preferably, H2 / H1 = 1 to 1.1.

[0045] To make it easier to understand, when H2 / H1=1, the sum of the thicknesses of the second well layer and the second barrier layer is equal to the sum of the thicknesses of the first well layer and the first barrier layer.

[0046] Preferably, the sum of the thicknesses H2 of the second well layer and the second barrier layer is greater than the sum of the thicknesses H1 of the first well layer and the first barrier layer. That is, H2 / H1 is preferably greater than 1. By employing a thick barrier + thin well structure in the green light emitting layer (i.e., the second light emitting layer 122), the distortion of the energy band can be reduced and the average energy band can be improved.

[0047] In some specific embodiments, the ratio H3 of the thicknesses of the second barrier layer to the second well layer is greater than or equal to the ratio H4 of the thicknesses of the first barrier layer to the first well layer (i.e., H3 ≥ H4), preferably the ratio H3 / H4 = 1 to 2, and includes, but is not limited to, any one point or range between any two of 1, 1.05, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2. This brings the average energy bands of the first light-emitting layer 121 and the second light-emitting layer 122 closer together, improving the luminous efficiency.

[0048] In some specific embodiments, the first barrier layer in the first light-emitting layer 121 includes at least one of GaN, AlGaN, or InAlGaN.

[0049] In some specific embodiments, the second barrier layer in the second light-emitting layer 122 comprises at least one of GaN, AlGaN, or InAlGaN. Here, the compositions of the first barrier layer and the second barrier layer may be the same or different, and the present invention is not limited thereto.

[0050] In some specific embodiments, the number of the first well layers is 10 to 20, preferably 10 to 15, and a first barrier layer is provided between two adjacent first well layers.

[0051] In some specific embodiments, the number of the second well layers is 1 to 5, preferably 1 to 3, and the upper and lower sides adjacent to any second well layer are both second barrier layers.

[0052] In some specific embodiments, the first light-emitting layer 121 includes a first periodic structure in which a first well layer and a first barrier layer are alternately stacked, preferably the number of periods of the first periodic structure is 10 to 20, and includes, but is not limited to, any one point or range between any two of 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20.

[0053] In some specific embodiments, the second light-emitting layer 122 includes a second periodic structure in which a second well layer and a second barrier layer are alternately stacked, more preferably the number of periods of the second periodic structure is 1 to 5, including, but not limited to, any one point of 1, 2, 3, 4, 5, or a range value between any two of them.

[0054] In some specific embodiments, the number of the first well layers is 4 to 20 times the number of the second well layers, and includes, but is not limited to, any one point or range between any two of 4, 5, 6, 7, 8, 10, 12, 13, 14, 15, 16, 18, and 20 times. Preferably, it is 6 to 15 times.

[0055] In some specific embodiments, as shown in Figure 3, the multicolor light-emitting layer 120 includes nine first well layers (denoted as W1) and one second well layer (denoted as W2), i.e., a total of ten light-emitting well layers, with a light-emitting barrier layer provided between two adjacent light-emitting well layers. Here, the nine first well layers are close to the N-type layer 110 and emit blue light. The one second well layer is closest to the P-type layer 130 and emits green light. Here, the In concentration in the second well layer is greater than the In concentration in the first well layer, and the thickness of the second well layer is smaller than the thickness of the first well layer. Both the first well layer W1 and the second well layer W2 are made of InGaN material, the difference being that the In content in the second well layer is greater than the In content in the first well layer so that the first and second well layers emit light of different wavelengths. A first barrier layer (denoted as B1) is provided between two adjacent first well layers, and between the last first well layer and the first second well layer. A second barrier layer (denoted as B2) is provided between the second well layer and the P-type layer 130, with the thickness of the second barrier layer being greater than that of the first barrier layer. Both the first and second barrier layers are GaN layers.

[0056] In some specific embodiments, as shown in Figure 4, the multicolor light-emitting layer 120 includes 12 first well layers (denoted as W1) and 1 second well layer (denoted as W2), i.e., a total of 13 light-emitting well layers. Here, the 12 first well layers closest to the N-type layer 110 are blue light well layers. The 1 second well layer closest to the P-type layer 130 is a green light well layer. A first barrier layer (denoted as B1) is provided between two adjacent first well layers. A second barrier layer (denoted as B2) is provided on the side of the second well layer closest to the P-type layer 130. The thickness of the second well layer is smaller than the thickness of the first well layer, and the number of first well layers W1 is 12 times the number of second well layers W2. The sum of the thicknesses of a pair of second barrier layers and second well layers H2 is greater than the sum of the thicknesses of a pair of first barrier layers and first well layers H1, i.e., H2 / H1 is greater than 1. The thickness of the second barrier layer is greater than the thickness of the first barrier layer. Both the first and second barrier layers are GaN layers.

[0057] In some specific embodiments, the energy band of the second well layer in the second light-emitting layer 122 is lower than the energy band of the first well layer in the first light-emitting layer 121. This makes the emission wavelength of the second light-emitting layer 122 longer than that of the first light-emitting layer 121.

[0058] In some specific embodiments, the energy band of the second barrier layer in the second light-emitting layer 122 is lower than the energy band of the first barrier layer in the first light-emitting layer 121. This reduces the quantum confinement Stark effect (QCSE effect) in the second light-emitting layer 122.

[0059] In some specific embodiments, the first barrier layer is an AlGaN+GaN blue light barrier layer, for example, by growing GaN first, then AlGaN, and then GaN again. The second barrier layer is a GaN green light barrier layer, which may also contain AlGaN, and its Al content is lower than that of the first barrier layer.

[0060] In some specific embodiments, as shown in Figure 5, the multicolor light-emitting layer 120 includes 12 first well layers and 1 second well layer, i.e., a total of 13 light-emitting well layers. The thickness of the second well layer is smaller than the thickness of the first well layer, and the number of first well layers is 12 times the number of second well layers. The first light-emitting layer 121 is provided at the edge near the N-type layer 110, and the second light-emitting layer 122 is provided at the edge near the P-type layer 130. A second barrier layer (denoted as B2) is provided on both sides of the second well layer. At least one set of energy levels of the first barrier layer (denoted as B1) between adjacent first well layers is higher than the energy level of the second barrier layer. For example, at least one first barrier layer is an AlGaN layer or an InAlGaN layer, and the second barrier layer is a GaN layer. The thickness of the second barrier layer is greater than the thickness of the first barrier layer.

[0061] In some specific embodiments, if the direction from the N-type layer 110 to the P-type layer 130 is defined as the first direction, the energy band of the second barrier layer is from low to high in the first direction, for example, by growing GaN first, then AlGaN, or by growing InGaN with a low In composition first, then GaN. This can improve the quantum confinement Stark effect (QCSE effect) in the second light-emitting layer 122.

[0062] In some specific embodiments, the energy band of the first barrier layer is from high to low in a first direction, for example, growing AlGaN first and then GaN, or growing GaN first and then InGaN with a low In composition. This can improve the quality of the growth interface between the barrier layer and the well layer in the first light-emitting layer 121.

[0063] In some specific embodiments, Al is doped between the second well layer and the second barrier layer in the second light-emitting layer 122. That is, a small amount of Al is doped at the intersection of the second well layer and the second barrier layer in the second light-emitting layer 122. This can reduce the leakage current of the device.

[0064] In some specific embodiments, the thickness of Al is less than one-third of the thickness of the second well layer.

[0065] In some specific embodiments, when the injection current is 350 mA, the luminance of the monolithic multicolor light-emitting diode is 770 mW or more, specifically including, but not limited to, one point or any two of the following values: 770 mW, 775 mW, 780 mW, 785 mW, 790 mW, 800 mW, and / or a range between them. Preferably, it is 770 to 790 mW.

[0066] In some specific embodiments, as shown in Figure 6, the first light-emitting layer 121 is provided at the end closest to the N-type layer 110, and the second light-emitting layer 122 is provided at the end closest to the P-type layer 130. A first barrier layer is provided between two adjacent first well layers, and a second barrier layer is provided on the side of the second well layer closest to the P-type layer 130. Here, the first barrier layer has a GaN / AlGaN / GaN structure (the convex portion in Figure 6 is AlGaN, and the inclusion of Al increases the energy level, thereby increasing the blocking ability of the blocking layer as a barrier layer), and the second barrier layer is GaN.

[0067] In some specific embodiments, the second light-emitting layer 122 may be located between the N-type layer 110 and the first light-emitting layer 121, in addition to being located between the first light-emitting layer 121 and the P-type layer 130. As shown in Figure 7, the second light-emitting layer 122, which emits long-wavelength light, is closer to the N-type layer 110 and includes several alternately stacked second well layers W2 and second barrier layers B2, while the first light-emitting layer, which emits relatively short-wavelength light, is closer to the P-type layer 130 and includes several alternately stacked first well layers W1 and first barrier layers B1. Here, the thickness of the second well layer W2 is smaller than the thickness of the first well layer W1, and the thickness of the second barrier layer B2 is larger than the thickness of the first barrier layer B1. At the same time, the sum of the thicknesses of the first barrier layers and first well layers in one period is smaller than the sum of the thicknesses of the second barrier layers and second well layers in one period. The number of well layers in the first layer is greater than that of the second layer, and the luminescence intensity of the first luminescent layer 121 is greater than that of the second luminescent layer 122.

[0068] In some specific embodiments, as shown in Figure 8, the second light-emitting layer 122 is located midway between the first light-emitting layer 121.

[0069] The relative positions of the first light-emitting layer 121 and the second light-emitting layer 122 are related to the number of second well layers. When the number of second well layers (green light wells) is greater than 3, the second light-emitting layer 122 is provided at the end closer to the N-type layer 110, and when the number of second well layers (green light wells) is less than 3, the second light-emitting layer 122 is provided at the end closer to the P-type layer 130.

[0070] In some specific embodiments, as shown in Figure 9, the epitaxial structure layer of the monolithic multicolor light-emitting diode includes at least one substrate 100 and a first buffer layer 101, an N-type layer 110, a second buffer layer 102, a third buffer layer 103, a first light-emitting layer 121, a second light-emitting layer 122, and a P-type layer 130 grown sequentially on the substrate 100. Here, the substrate 100 includes sapphire substrate 100, silicon substrate 100, GaN substrate 100, GaAs substrate 100, etc., and the first buffer layer 101 is at least one of AlN layer, GaN layer, and AlGaN layer, and when the substrate material 100 and the N-type material do not match, for example when the substrate 100 is sapphire, it is used to mitigate the lattice mismatch between the sapphire substrate 100 and the N-type layer 110, and the N-type layer 110 is usually a nitride semiconductor layer doped with n-type impurities to supply electrons, for example, a Si-doped GaN layer, and the second buffer layer 102 and the third buffer Layer 103 is located between the multicolor emissive layer 120 and the N-type layer 110 and plays a buffering and transition role. The second buffer layer 102 and the third buffer layer 103 are typically alternating InGaN and GaN layers, where the In content of the InGaN layer of the second buffer layer 102 is smaller than the In content of the InGaN layer of the third buffer layer 103, and the In content of the InGaN layer of the third buffer layer 103 is smaller than the In content in the well layer of the multicolor emissive layer 120. The P-type layer 130 is typically a nitride layer doped with P-type impurities to supply holes, such as a Mg-doped GaN layer.

[0071] In some specific embodiments, the epitaxial structure can be fabricated as a face-up chip, flip-chip chip, vertical chip, and high-voltage chip, depending on the chip structure type, and although the chip structure types differ, all include a P-electrode (P-PAD) electrically connected to the P-type layer 130 and an N-electrode electrically connected to the N-type GaN layer. The P-electrode and N-electrode are connected to an external power supply and emit light under the action of an applied current. The luminescence efficiency of the light-emitting layer differs with different currents.

[0072] Figure 10 shows a schematic diagram of the structure of a face-up LED chip, including a P-type electrode 230 electrically connected to a P-type layer 130, and an N-type electrode 240 electrically connected to an N-type layer 110. An insulating protective layer 250 is provided on the LED chip and has openings to expose the P-type electrode 230 and the N-type electrode 240. A current-blocking layer 210 is further provided between the P-type electrode 230 and the P-type layer 130, and an ohmic contact layer 220 is provided on the current-blocking layer 210. The current-blocking layer 210 is a film layer formed from one or more materials selected from SiO2, SiN2, Al2O3, and TiO2, and its shape is basically the same as the shape of the P-electrode. The ohmic contact layer 220 is usually one or more conductive transparent film layers or conductive reflective film layers, and in face-up products it is a transparent conductive film layer or ITO.

[0073] Figure 11 shows a schematic diagram of the structure of a flip-chip LED chip. In the flip-chip structure, the ohmic contact layer 220 can be one or more layers selected from an ITO transparent conductive layer, an Ag reflective layer, or an Al reflective layer, for example, an ITO layer and an Ag reflective layer. The insulating protective layer 250 and the current blocking layer 210 can be single-layer protective film layers, or they can include a distributed Bragg reflective layer. The second P electrode 262 and the second N electrode 272 are electrically connected to the first P electrode 261 and the first N electrode 271, respectively, through openings in the insulating protective layer.

[0074] In some specific embodiments, with a chip size of 25 × 51 mil² and an injection current of 350 mA, the brightness of a single blue light LED chip is 890-900 mW, the brightness of a blue-green light LED chip with blue light wells (i.e., first well layer) and green light wells (i.e., second well layer) of equal thickness is 680-700 mW, and the brightness of a blue-green LED chip with the structure of the present invention (thin green light well, i.e., thickness of second well layer < thickness of first well layer) is 770-790 mW. It has been found that the brightness of the monolithic multicolor light-emitting diode chip provided by the present invention is superior to that of a blue-green light LED chip with blue light wells and green light wells of equal thickness, with a brightness improvement of at least 10%.

[0075] In a second embodiment, the present invention provides an LED backlight, the LED backlight comprising an RGB-LED and a white LED, wherein the RGB-LED or the white LED comprises the monolithic multicolor light-emitting diode described above.

[0076] In some specific embodiments, the RGB-LED includes the monolithic multicolor light-emitting diode and the monocolor red light-emitting diode.

[0077] In some specific embodiments, the white LED is formed by combining the monolithic multicolor light-emitting diode and fluorescent powder.

[0078] In some specific embodiments, the white LED includes the monolithic multicolor light-emitting diode, a fluorescent film layer, and a reflective sealing layer provided around (on all four sides of) the monolithic multicolor light-emitting diode and the fluorescent film layer. Here, the fluorescent film layer includes a silicone layer and a red fluorescent layer.

[0079] White LEDs are formed by packaging monolithic multicolor light-emitting diodes, and as shown in Figure 12, they are chip-scale packages. A fluorescent film layer is provided on the light-emitting surface of a flip-chip blue-green two-wavelength LED chip, and a reflective sealing layer is provided around the fluorescent film layer and the four sides of the LED chip. Here, the fluorescent film layer is a wavelength conversion film layer formed by mixing silicone and a red fluorescent film.

[0080] In some specific embodiments, the red fluorescent powder in the red fluorescent layer includes nitride fluorescent powder and / or fluoride fluorescent powder.

[0081] In some specific embodiments, when the red fluorescent powder is a fluoride fluorescent powder, a silicone protective layer is further provided on the side of the red fluorescent layer furthest from the monolithic multicolor light-emitting diode.

[0082] When the fluorescent powder is a KSF fluorescent film, in order to protect the KSF fluorescent film layer, a transparent silicone protective layer can be first provided on the light-emitting surface of the fluorescent film layer, and then a reflective sealing layer can be provided (as shown in Figure 13). Here, the KSF fluorescent powder (K2SiF6:Mn 4+ ) belongs to the fluoride-based fluorescent powder category, and severe degradation occurs in both high-temperature, high-humidity and high-temperature environments, manifesting as brightness reduction and color shift. The present invention solves the problem that "KSF fluorescent powder undergoes severe degradation in high-temperature, high-humidity and high-temperature environments, leading to brightness reduction and color shift" by providing a transparent silicone protective layer.

[0083] In some specific embodiments, when the input current is 10 mA or more, the ratio of the peak wavelength intensity of the first color light (blue light) to the peak wavelength intensity of the second color light (green light) is 5 or more, preferably 5 to 10. After a red fluorescent film layer is applied to the surface of a blue-green dual-wavelength LED chip, a white LED is formed through packaging. In the process of forming a white spectrum, some blue light excites red fluorescence to form red light. Therefore, in the spectrum of the white LED, the peak intensity of blue light clearly decreases, but the peak intensity of the green light spectrum remains basically unchanged. In order to satisfy the wide color gamut of the white LED, the peak intensity of blue light in the white light spectrum also needs to meet a certain requirement. Therefore, when installing a blue-green dual-wavelength LED chip, it is necessary to set the ratio of the peak intensity of the blue light wavelength to the peak intensity of the green light wavelength. Figure 14 shows the optical power spectrum distribution under different currents.

[0084] Figure 15 shows the normalized relative intensity spectra for green light. Here, curve 1 is the spectral curve for a single blue light LED chip + green powder + red powder, curve 2 is the spectral curve for a blue-green two-color LED chip, and curve 3 is the spectral curve for a blue-green two-color LED chip + red fluorescent powder. Comparing curve 1 and curve 3, the full width at half maximum of the green light spectrum of curve 3 is clearly smaller than that of curve 1. Comparing curve 2 and curve 3, the peak intensity of the blue light is weaker, and the peak intensity of the green light is basically unchanged, so it can be determined that the blue light is mainly exciting the red fluorescent powder.

[0085] While the present invention has been described and explained using specific examples, it should be recognized that these examples are merely for illustrating the technical means of the present invention and do not limit them. Those skilled in the art should understand that modifications may be made to the technical means described in the aforementioned examples, or that some or all of the technical features therein may be replaced by equivalent substitutions, without departing from the spirit and scope of the invention. These modifications or substitutions do not cause the essence of the corresponding technical means to deviate from the scope of the technical means of each example of the present invention. Therefore, this means that all such substitutions and modifications within the scope of the present invention are included in the appended claims. [Explanation of Symbols]

[0086] 100 circuit boards 101 First buffer layer 102 Second buffer layer 103 Third buffer layer 110 N-type layer 120 Multicolor Emitting Layer 121 First light-emitting layer 122 Second light-emitting layer 130 P type layer 210 Current blocking layer 220 Ohmic Contact Layer 230 P type electrode 240 N-type electrode 250 Insulating protective layer 261 First P electrode 262 Second P electrode 271 First N electrode 272 Second N electrode

Claims

1. A monolithic multicolor light-emitting diode comprising a multicolor light-emitting layer provided between an N-type layer and a P-type layer, The multi-color light-emitting layer includes a first light-emitting layer that emits light of a first color and a second light-emitting layer that emits light of a second color, wherein the peak wavelength λ of the light of the second color is ｐ２ The peak wavelength λ of the first color of light is ｐ１ Larger than, and λ ｐ２ -λ ｐ１ ≥ 50 nm, A monolithic multicolor light-emitting diode characterized in that the thickness of the second well layer in the second light-emitting layer is less than the thickness of the first well layer in the first light-emitting layer.

2. The monolithic multicolor light-emitting diode according to claim 1, characterized in that it satisfies at least one of the following conditions. (1) The ratio of the thickness of the second well layer to the first well layer is 0.5 to 0.

95. (2) The thickness of the second well layer is 27 to 32 Å. (3) The thickness of the first well layer is 33 to 38 Å.

3. The first well layer contains In ｘ１ Ga （１－ｘ１） N, and the second well layer contains In ｘ２ Ga （１－ｘ２） N, where 1 > X ２ > X １ > 0.1, and the monolithic multicolor light-emitting diode according to claim 1, characterized in that.

4. The aforementioned X ２ = 0.22 to 0.28, and / or the above X １ The monolithic multicolor light-emitting diode according to claim 3, characterized in that the value is 0.13 to 0.

19.

5. The monolithic multicolor light-emitting diode according to claim 1, characterized in that it satisfies at least one of the following conditions. (1) The first color of light includes blue light, and the second color of light includes green light. (2) Peak wavelength λ of the first color of light ｐ１ This corresponds to 440-470 nm. (3) Peak wavelength λ of the second color of light ｐ２ This corresponds to 520-550 nm. (4) When the input current is 10 mA or more, the ratio of the peak wavelength intensity of the first color light to the peak wavelength intensity of the second color light is 5 or more.

6. The monolithic multicolor light-emitting diode according to claim 1, characterized in that the second light-emitting layer includes a second barrier layer, the first light-emitting layer includes a first barrier layer, and the monolithic multicolor light-emitting diode satisfies at least one of the following conditions. (1) The thickness of the second barrier layer is greater than the thickness of the first barrier layer. (2) The thickness of the second barrier layer is 100 to 200 Å. (3) The thickness of the first barrier layer is 90 to 100 Å. (4) The ratio H2 of the sum of the thicknesses of the second well layer and the second barrier layer to H1 of the sum of the thicknesses of the first well layer and the first barrier layer is H2 / H1 = 0.9 to 1.

1. (5) The ratio H3 of the thickness of the second barrier layer to the second well layer is equal to or greater than the ratio H4 of the thickness of the first barrier layer to the first well layer, and H3 / H4 = 1 to 2.

7. The first barrier layer in the first light-emitting layer comprises at least one of GaN, AlGaN, or InAlGaN. and / or, the second barrier layer in the second light-emitting layer comprises at least one of GaN, AlGaN, or InAlGaN, characterized in that the monolithic multicolor light-emitting diode according to claim 1.

8. The number of the first well layers is 10 to 20, and a first barrier layer is provided between two adjacent first well layers. The monolithic multicolor light-emitting diode according to claim 1, characterized in that and / or the number of the second well layers is 1 to 5, and a second barrier layer is provided on both sides of each of the second well layers.

9. The first light-emitting layer includes a first periodic structure in which a first well layer and a first barrier layer are alternately stacked, and the number of periods of the first periodic structure is 10 to 20. and / or, the monolithic multicolor light-emitting diode according to claim 1, wherein the second light-emitting layer includes a second periodic structure in which a second well layer and a second barrier layer are alternately stacked, and the number of periods of the second periodic structure is 1 to 5.

10. The monolithic multicolor light-emitting diode according to claim 8, characterized in that the number of the first well layers is 4 to 20 times the number of the second well layers.

11. The monolithic multicolor light-emitting diode according to claim 1, characterized in that it satisfies at least one of the following conditions. (1) The energy band of the second well layer in the second light-emitting layer is lower than the energy band of the first well layer in the first light-emitting layer. (2) The energy band of the second barrier layer in the second light-emitting layer is lower than the energy band of the first barrier layer in the first light-emitting layer. (3) The direction from the N-type layer to the P-type layer is defined as the first direction, the energy band of the second barrier layer in the second light-emitting layer changes from low to high in the first direction, and the energy band of the first barrier layer in the first light-emitting layer changes from high to low in the first direction.

12. Al is doped between the second well layer and the second barrier layer in the second light-emitting layer. The monolithic multicolor light-emitting diode according to claim 1, characterized in that the thickness of the Al-doped region is less than one-third of the thickness of the second well layer.

13. The monolithic multicolor light-emitting diode according to claim 1, characterized in that when the injection current is 350 mA, the brightness of the monolithic multicolor light-emitting diode is 770 mW or more.

14. An LED backlight including RGB-LEDs and white LEDs, The LED backlight is characterized in that the RGB-LED or the white LED includes a monolithic multicolor light-emitting diode as described in any one of claims 1 to 13.

15. The LED backlight according to claim 14, characterized in that it satisfies at least one of the following conditions. (1) The RGB-LED includes the monolithic multicolor light-emitting diode and the monocolor red light-emitting diode. (2) The white LED includes the monolithic multicolor light-emitting diode, a fluorescent film layer, and a reflective sealing layer provided around the monolithic multicolor light-emitting diode and the fluorescent film layer. (Here, the fluorescent film layer includes a silicone layer and a red fluorescent layer, the red fluorescent powder in the red fluorescent layer includes nitride fluorescent powder and / or fluoride fluorescent powder, and if the red fluorescent powder is fluoride fluorescent powder, a silicone protective layer is further provided on the side of the red fluorescent layer furthest from the monolithic multicolor light-emitting diode.)

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